Can having a yeast infection make your lower abdomen hurt a little bit and lower back?

Not likely: Vaginal yeast causes genital irritation and itching and sometimes a little thick, cheesy discharge. But not abdominal or back pain. If you're having more vaginal discharge, vaginal odor, or colored discharge, I would be worried about an STD that might have progressed to fallopian tube infection (pelvic inflammatory disease, PID). See a doctor soon -- do it immediately if pain severe or any fever.